Such devices, in particular in the form of an adjusting ring, are used in electric tools which are operated on alternating current (AC) or direct current (DC). These electric tools can be provided with an electronics controller. The electric motor for the electric hand tool can be a brushless (EC) motor.
EP 0 778 655 A2 has disclosed a device for adjusting the carbon brushes in the form of an adjusting ring for a reversible electric motor with a base and with a mount mounted pivotably on the base. Brush holders for the carbon brushes wiping over the collector of the electric motor are arranged on the mount. The adjusting ring therefore acts as a holder for the carbon brushes of the mechanical commutator of the electric motor. Rotation of the adjusting ring brings about a change in the direction of rotation of the electrical machine. Furthermore, the adjusting ring enables optimum commutation in the case of counterclockwise and/or clockwise rotation of the electric motor, as a result of which a reduction in the brush sparking and radio interference and a longer life of the carbon brushes are achieved.
In electric tools, the electric motor can often be driven by means of power electronics, such as a pulse width controller, a phase gating controller, a phase chopping controller or the like. The power electronics can be arranged on a printed circuit board as a separate component part at an expedient point in the housing of the electric tool, for example in the handle of the electric tool. Electrical switches located in the handle for electric tools are also known, for example, in which the power electronics are arranged in the switch housing. Since the commutation advantageously takes place directly on the electric motor, the brushes and the collector are cooled effectively thanks to the flow from the motor fan. On the other hand, the power adjustment generally takes place in the handle or in the switch housing. It is difficult for the heat to be dissipated here owing to the low level of or lack of air flow.